[C/C++] std::memcpy Api Reference

std::memcpy

void* memcpy( void* dest, const void* src, std::size_t count ); Defined in header <cstring>

Parameters

dest	-	pointer to the memory location to copy to
src	-	pointer to the memory location to copy from
count	-	number of bytes to copy

Return value

dest




Example

#include <iostream>
#include <cstdint>
#include <cstring>
 
int main()
{
    // simple usage
    char source[] = "once upon a midnight dreary...", dest[4];
    std::memcpy(dest, source, sizeof dest);
    for (char c : dest)
        std::cout << c << '\n';
 
    // reinterpreting
    double d = 0.1;
//  std::int64_t n = *reinterpret_cast<std::int64_t*>(&d); // aliasing violation
    std::int64_t n;
    std::memcpy(&n, &d, sizeof d); // OK
 
    std::cout << std::hexfloat << d << " is " << std::hex << n
              << " as an std::int64_t\n";
}

Result

o
n
c
e
0x1.999999999999ap-4 is 3fb999999999999a as an std::int64_t

Ref : 

http://en.cppreference.com/w/cpp/string/byte/memcpy